Due to advance in a communication system, various types of wireless terminals have been introduced to consumers, such as companies and individuals. The current 3rd generation partnership project (3GPP) family of mobile communication systems, such as LTE (Long Term Evolution) or LTE-Advanced, is a high-speed and large-capacity communication system. Such a communication system can provide a service for transmitting and receiving a various types of data, such as images or wireless data, as well as a voice data. Accordingly, there is demand for developing technology for transmitting a large amount of data at a high speed as fast as transmission in a wired communication network. For transmitting a large amount of data at a high speed, data may be efficiently transmitted by using a plurality of cells.
However, a base station has a limitation to provide a communication service to a plurality of terminals. For example, a base station uses limited frequency resources to provide a communication service to a plurality of terminals with a large amount of data. Because of the limited frequency resources, a communication service provider (e.g., carrier) needs to secure exclusive frequency resources, and such securement of frequency resources may require a high cost.
Meanwhile, an unlicensed frequency band is not allowed to be exclusively used by a specific communication service provider. The unlicensed frequency band may be shared by a plurality of communication service providers or communication systems. For example, a wireless local area network (WLAN) technology (e.g., WiFi) provides a data transmission/reception service by using frequency resources of the unlicensed band.
Therefore, it is required to develop technology for enabling a mobile communication system to transmit and receive data by using an access point (AP) of the corresponding WiFi.